<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
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<body>
    <script>
        var a = 10;
        while(a < 20){
            console.log(a);
            // 需要改变a的值
            a++;
        }


    </script>
</body>
</html>